In terms of function and genetics, DnaK is the best characterized member of the Hsc70 family, the members of which function as chaperones to allow efficient folding of proteins in the otherwise challenging intracellular environment. Others in our lab have isolated a number of mutants in the dnaK gene of E. coli. These mutants differ in their in vivo and in vitro phenotypes with regard to dominance, ATP binding, sensitivity to anions interactions with other chaperones, and control of the heat shock response. The coordinates of a DnaK homologue, Bovine HSC70 are available. I have used these coordinates to examine the structural consequences of several of our mutants. In particular, the A174T mutant of DnaK has properties indicating that it may be defective in undergoing a conformational change upon ATP hydrolysis. The model reveals that that this substitution is in a highly conserved residue at the interface between a surface helix and a beta-sheet abutting the ATP binding pocket. This region has been proposed to undergo a conformational change upon ATP binding, and Won Chul Suh, in our lab, has evidence that the surface helix is in close proximity to the binding site for DnaJ, a factor which greatly accelerates ATP hydrolyis by DnaK. We continue to use the modelling facilities of the Computer Graphics Laboratory to examine additional mutants and to design site-directed mutants in DnaK.